This invention pertains to detection systems including a weight and balance system for an aircraft or the like which measures the bend in a member which is caused to bend by the weight on the aircraft by means of inclinometers and, more particularly, servoed accelerometers mounted to the member and which have signal outputs representing the angle of the member with respect to a reference plane and which are utilized to determine the angle of bend in the member as a indication of weight supported thereby.
A pilot in command of an aircraft must, before each flight, determine that the aircraft's weight and balance are within the safe operating limits or boundaries of the aircraft. This is typically accomplished by calculating the total airplane weight and the distribution of that weight in order to determine balance or center of gravity. The weight and balance determination is usually made by auditing a list of cargo, fuel, passengers, oil and crew members, there frequently being estimation of passenger and crew member weight and distribution thereof. Cargo may be actually weighed or estimated. Fuel weight is determined by quantity added to the aircraft and its temperature estimated to give an approximate fuel weight. All of this is then added to the basic empty weight and distribution of the empty weight of the aircraft as determined at either the date of manufacture or by subsequent weighing on scales.
Naturally, there are errors in such estimates and human calculations but, for the majority of flights, the built-in safety factors including extra runway length and better than minimum airplane performance and control are adequate to cover these errors. Even so, there have been many examples of past incidents and accidents where it was later determined that large errors in weight and balance were not detected by the pilots. In air freight operations, there is a large variation in loads, types of cargo, fuel and airport conditions whereby there is a much greater possibility for a serious error.
To further improve flight safety, an onboard weight and balance system allows the pilots to cross-check data on load and fuel normally provided by others. With sufficient accuracy and reliability, the onboard weight and balance system can be the primary instrument for the determination of weight and balance. The system can assist in positioning cargo at a more nominal balance point to reduce aerodynamic drag which results in economic savings because of reduced use of fuel with adequate flight control stability margins for the pilots.
In recent years, several onboard weight and balance systems have been developed for use on aircraft, including the use of strain gages and pressure and magnetic variable reluctance sensors. They have not measured up to expectations because of problems in stability, accuracy, reliability and ability to survive in a harsh environment. Because of these problems, many or most of these systems have been disconnected or removed.
An added safety factor in aircraft operation is a full complement of properly pressurized landing gear tires which has required visual inspection and which can be difficult to accomplish under conditions such as extreme winter weather.